In recent years, the BCT, an existing highway safety device, has been found to pose a hazard to motorists.
The BCT is an end treatment for guardrail systems. It is designed to prevent vehicles from directly impacting the end of a guardrail, which, being stiff, strong, and blunt, would be a large hazard if left unshielded. In addition, this device transfers, to foundation anchors in the soil, a sizable tensile force which develops in the rail when a vehicle impacts the guardrail "downstream" and is redirected.
Originally, this device functioned satisfactorily but, as cars became lighter in weight, safety problems were exposed. During end-on impacts of heavy vehicles with the BCT, the flared guardrail is bent and regions of highly localized plastic deformation develop, resulting in a kinematic rotation of the guardrail in front of the vehicle. However, light vehicles do not have sufficient energy to create these plastic rotation points and the guardrail often "spears" the vehicle through a window or door panel. An attempt to improve the response, by weakening the guardrail at specific locations, has the deleterious side effect of promoting vehicle snagging during side-on impact of the BCT.
The safety hazards of the BCT often result in death and severe injuries. The Federal government is currently considering a ban on the use of BCTs on federally-funded highway projects. Over 160,000 BCTs are currently in place on highways built with federal funds; many more have been placed on state and county roads.
Due to the poor behavior of the BCT under end-on impacts, a quick release system is needed for retrofitting currently installed units and for modifying future units.